Toothed belts formed mainly of thermoplastic material and method of making

ABSTRACT

A toothed belt construction formed mainly of thermoplastic material and method of making the same are provided, the method including the steps of disposing at least one layer of the thermoplastic material about the outer peripheral surface of a building drum that has the outer peripheral surface thereof defined by alternating teeth and grooves, and then forcing the one layer of thermoplastic material toward the drum while the temperature of the one layer of thermoplastic material is above its softening temperature and below its melting temperature so as to cause at least part of the one layer of thermoplastic material to exude into the grooves to form at least part of the plurality of teeth of the belt construction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 844,361,filed Mar. 2, 1992, now abandoned in favor of said continuation patentapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new belt construction and to a new method ofmaking the same.

2. Prior Art Statement

It is known to provide a toothed belt construction formed mainly ofthermoplastic material wherein the belt construction is made byinjection molding the thermoplastic material after the thermoplasticmaterial has been heated to a temperature above its melting temperature.

It is also known to form a belt construction of uncured rubber materialby disposing at least one layer of the uncured rubber material about theouter peripheral surface of a building drum that has the outerperipheral surface thereof defined by alternating teeth and grooves, andthen forcing the one layer of uncured rubber material toward the drumwhile the temperature of the one layer of uncured rubber material isabove a certain softening temperature thereof and below a vulcanizingtemperature thereof so as to cause at least part of the one layer ofuncured rubber material to exude into the grooves to form at least partof the plurality of teeth of the belt construction. For example, see theU.S. Pat. No. 3,078,206 to Skura, and the U.S. Pat. No. 4,583,963 toMarsh et al.

However, it is applicants' belief that it is not known that a toothedbelt construction formed mainly of thermoplastic material can be formedby the method of the aforementioned U.S. Pat. No. 3,078,206 to Skura.

SUMMARY OF THE INVENTION

It is one feature of this invention to provide a new toothed beltconstruction formed mainly of thermoplastic material without utilizingan injection molding process or a high pressure compression moldingoperation wherein the thermoplastic material must be in the molten statethereof.

In particular, it was found according to the teachings of this inventionthat a conventional building drum arrangement for forming toothed beltconstructions from uncured rubber layers can be utilized to form toothedbelt constructions formed mainly of thermoplastic material if thetemperature of the thermoplastic material is maintained at a temperatureabove its softening temperature and below its melting temperature.

For example, one embodiment of this invention comprises a method ofmaking a belt construction mainly of thermoplastic material and havingopposed sides one of which comprises a plurality of teeth, the methodcomprising the steps of disposing at least one layer of thethermoplastic material about the outer peripheral surface of a buildingdrum that has the outer peripheral surface thereof defined byalternating teeth and grooves, and then forcing the one layer ofthermoplastic material toward the drum while the temperature of the onelayer of thermoplastic material is above its softening temperature andbelow its melting temperature so as to cause at least part of the onelayer of thermoplastic material to exude into the grooves to form atleast part of the plurality of teeth.

Accordingly, it is an object of this invention to provide a new methodof making a belt construction mainly of thermoplastic material, themethod of this invention having one or more of the novel features ofthis invention as set forth above or hereinafter shown or described.

Another object of this invention is to provide a new belt constructionformed mainly of thermoplastic material, the belt construction of thisinvention having one or more of the novel features of this invention asset forth above or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and where in:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view illustrating the new beltconstruction of this invention.

FIG. 2 is a perspective view illustrating how the belt construction ofFIG. 1 is formed on a building drum arrangement.

FIG. 3 is a cross-sectional view illustrating the building drum of FIG.2 disposed in a container for applying steam and pressure to thebuilding drum.

FIG. 4 is an enlarged fragmentary cross-sectional view taken on line4--4 of FIG. 2.

FIG. 5 is a view similar to FIG. 4 and illustrates another embodiment ofthe method of this invention.

FIG. 6 is a view similar to FIG. 4 and illustrates the material on thebuilding drum after the same has been forced toward the building drum bysteam and pressure.

FIG. 7 is a view similar to FIG. 1 and illustrates another new beltconstruction of this invention.

FIG. 8 is a view similar to FIG. 2 and illustrates how the material forforming the belt construction of FIG. 7 is disposed on a building drum.

FIG. 9 is an enlarged fragmentary cross-sectional view taken on line9--9 of FIG. 8.

FIG. 10 is a view similar to FIG. 9 and illustrates how the material onthe building drum of FIG. 8 is subsequently formed on the building drumto provide the belt construction of this invention that is set forth inFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the various features of this invention are hereinafter illustratedand described as being particularly adapted to provide toothed beltconstructions having a particular profile for the teeth thereof, it isto be understood that the various features of this invention can beutilized singly or in various combinations thereof to provide beltconstructions with teeth having other shapes as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate some of the wide variety of uses of this invention.

Referring now to FIG. 1, the new belt construction of this invention isgenerally indicated by the reference numeral 20 and comprises a beltbody 21 formed of thermoplastic material, that had initially comprisedone or more layers of like or dissimilar thermoplastic materials asdesired, and defining opposed surface means 22 and 23 with the surfacemeans 22 being generally flat while the surface means 23 defines aplurality of teeth 24 which in the embodiment illustrated in FIG. 1 haveangled sides 25 and 26 and substantially flat bottoms 27.

The belt construction 20 further comprises a reinforcing tensile means28 formed from one or more reinforcing cords of any suitable material,such as thermoplastic material, and arranged in a helical manner in amanner well known in the art and hereinafter set forth.

In addition, the belt construction 20 also comprises a fabric means 29that generally lines the surfaces 25, 26 and 27 of the teeth 24 as wellas the land areas 30 between the teeth 24 all in a manner well known inthe art and for well known purposes. For example, see the aforementionedU.S. Pat. No. 4,583,063 to Marsh et al, whereby this U.S. patent isbeing incorporated into this disclosure by this reference thereto.

As previously stated, the belt construction 20 of this invention isuniquely formed by utilizing the well known building drum and containerarrangement of the aforementioned U.S. Pat. No. 3,078,206 to Skura,whereby this U. S. patent is also being incorporated into thisdisclosure by this reference thereto.

Such prior known apparatus is generally indicated by the referencenumeral 31 in FIG. 3 and comprises a generally cylindrical building drum32 formed of metallic material and being adapted to be disposed within ametallic container 33 which is adapted to have steam injected into acavity 34 thereof through suitable valve means 35. In addition, steamcan be injected into the container 33 through another valve means 36 inorder to heat the interior of the drum means 32 as well as to providemeans for venting liquid from the container 33 if desired.

Since the details of the structure and operation of the apparatus 31 iswell known, only the details thereof necessary to understand thefeatures of this invention will now be described.

As illustrated in FIG. 2, the building drum 32 has a plurality ofgrooves 37 and teeth 38 formed about the outer peripheral means 39thereof as illustrated, the grooves 37 to subsequently form the beltteeth 24 as will be apparent hereinafter and as illustrated in FIGS. 4and 6.

In order to form the belt construction 20 of this invention utilizingthe apparatus 31, a layer of the fabric means 29 is first disposed orwrapped on the outer peripheral surface 39 of the drum 32 in the mannerillustrated in FIGS. 2 and 4.

However, it is to be understood that the fabric means 29 could bepreformed so that the same would have teeth-shaped portions 29' asillustrated in FIG. 5 which initially line the grooves 37 of thebuilding drum as illustrated in FIG. 5 when the fabric means 29 isdisposed thereon.

Should the fabric means 29 not be preformed with the teeth-shapedportions 29' the fabric means 29 is formed of stretch material in amanner well known in the art so that the fabric means 29 will stretchand line the grooves 37 when forced therein by the exuding thermoplasticmaterial as will be apparent hereinafter and as illustrated in FIG. 6.

In any event, after the fabric layer 29 is disposed on the drum 32, thetensile means 28 is helically wrapped thereon in the manner illustratedin FIG. 2 with the spacing between the adjacent coils 28' of the tensilemeans 28 being any desired amount as is well known in the art.

Thereafter, the thermoplastic material 21 is disposed or wrapped on thetensile means 28 in one or more layers thereof as desired and suchmaterial as illustrated in FIG. 2 could be so arranged that the same hasopposed ends 40 and 41 disposed in abutting relation to define alongitudinal seam 43 as illustrated.

Thereafter, a shrink cord 44 is wrapped on top of the thermoplasticmaterial 21 with or without an intermediate layer means of differentthermoplastic material and fabric means (not shown) between the shrinkcord 44 and the layer of thermoplastic material 21 for the purpose ofsubsequently applying pressure on the thermoplastic layer 21 in adirection that is radially toward the drum 32 as the shrink cord means44 is heated in a manner hereinafter set forth, the shrink cord 44 andany aforementioned intermediate layer means not forming a part of theresulting belt construction 20.

Of course, it is to be understood that other heat shrinkable means thanthe heat shrinkable cord 44 could be utilized for the same purpose, asdesired.

After the drum 32 has been wrapped in the manner illustrated in FIG. 2,the wrapped drum 32 can have a metallic or rubber-like bladder 45disposed around the same so that the bladder 45 will exert radiallyinward pressure on the material disposed on the drum 32 when pressurizedsteam is injected into the chamber 34 by the valve means 35, the valvemeans 36 as previously stated being adapted to heat the interior of thedrum 32 by injecting steam therein as desired.

In any event, the wrapped drum means 32 is heated to a temperature thatis above the softening temperature of the thermoplastic material 21 andbelow the melting temperature thereof and such temperature causes theshrink cord 44 to shrink and in combination with the steam pressureacting against the bladder 45 to collapse the bladder 45 toward the drum32, force the heated thermoplastic material 21 to exude between thecoils 28' of the tensile means 28 and force the fabric means 29 into thegrooves 37 of the drum 32 to form the teeth 24 as well as the remainderof the belt construction 20 in the manner illustrated in FIG. 6. Oncethe resulting belt sleeve has been formed on the drum 32 by thepreviously described heat and pressure, the drum 32 is removed from thecontainer 33 and allowed to cool so that the belt sleeve can then beremoved therefrom and the individual belt constructions 20 can be cuttherefrom all in a manner well known in the art.

While the belt construction 20 of this invention has been described asutilizing steam pressure and the shrink cord means 44 to exude theheated thermoplastic material 21 through the tensile means 28 to formthe teeth 24, it is to be understood that other means can be utilized toso force the heated thermoplastic material 21, such as a mechanical clamshell means etc., as long as the thermoplastic material 21 has beenheated to a temperature above its softening temperature and below itsmelting temperature.

For example, one belt construction that has been formed according to theteachings of this invention has the thermoplastic material 21 thereofcomprise a polyether blocked amide sold under the trademark "PEBAX" No.3533 by Atochem North America, Inc. of Philadelphia, Pa. Suchthermoplastic material has a softening point of approximately 165° F.and a melting point of approximately 306° F. It was found according tothe teachings of this invention that this thermoplastic material 21 bestformed the belt construction 20 of this invention when heated toapproximately 14° F. above the mid point of those two temperatures or toapproximately 250° F. for a time period of approximately 60 minutes whendisposed in the container 33 in the manner illustrated in the drawings.

It was found that when forming the belt construction 20 of theaforementioned "PEBAX" thermoplastic material and utilizing atemperature below the desired 250° F. temperature resulted in incompleteteeth 24 in the resulting belt construction and when formed at atemperature above the desired 250° F. temperature resulted in airentrapment in the resulting belt construction 20.

In order to provide the desired 250° F. temperature in the container 33,saturated steam at 30 psi absolute will create the temperature of 250°F.

The tensile means 28 in such belt construction comprise a dacron-type 52cord sold by the Du Pont Corporation of Wilmington, Del. and such cordhas a softening point of approximately 474° F. which is of course wellabove the temperature utilized to form the belt construction 20.

Similarly, the shrink cord can be any suitable material and in the aboveexample, the shrink cord comprised treated polyester 1000/2/3 cord whichhas a softening temperature well above the 250° F. utilized in formingthe belt construction 20.

Another belt construction 20 of this invention that was formed in theabove manner has the thermoplastic material 21 thereof comprising apolyterphthalate sold as Hytrel No. 5556 by the Du Pont Corporation ofWilmington, Del., such thermoplastic material having a softening pointof approximately 356° F. and a melting point of approximately 412° F. Itwas found that such belt construction 20 was formed best when thatparticular thermoplastic material was heated to approximately 5° F.above the softening point thereof or at approximately 361° F. Thistemperature can be created in the container 33 when the saturated steamis about 155 psi absolute.

Another belt construction 20 of this invention was formed from a lowdensity polyethylene film which had a softening point of approximately200° F. and a melting point believed to be above approximately 251° F.and formed best at a temperature of approximately 251° F.

Therefore, it can be seen that the normally used high steam pressure forthe container 33 forming belt constructions of uncured rubber materialsis not utilized by this invention, although it is to be understood thata high air pressure could be utilized together with other means ofheating the thermoplastic material, as a high steam pressure wouldproduce a temperature that is above the melting point temperature of thethermoplastic material.

While the belt construction 20 of this invention has been previouslydescribed as having the fabric means 29 and the tensile means 28, it isto be understood that one or both of the fabric means 29 and the tensilemeans 28 could be eliminated if desired.

For example, another thermoplastic belt construction of this inventionis generally indicated by the reference numeral 20A in FIGS. 7-10 andparts thereof similar to the belt construction 20 previously describedare indicated by like reference numerals followed by the referenceletter "A".

As illustrated in FIGS. 7-10, it can be seen that the belt construction20A can be formed in the same manner as the belt construction 20previously described except only the thermoplastic material 21A isutilized on the building drum 32A together with the shrink cord means44A so as to produce the teeth 24A all in the same manner as the beltconstruction 20 previously set forth whereby a further description ofthe details of the belt construction 20A and the method of forming thesame need not be set forth.

Therefore, it can be seen that this invention provides a new method ofmaking a belt construction mainly of thermoplastic material as well asproviding a new belt construction formed of thermoplastic material.

While the forms and methods of this invention now preferred have beenillustrated and described as required by the Patent Statute, it is to beunderstood that other forms and method steps can be utilized and stillfall within the scope of the appended claims wherein each claim setsforth what is believed to be known in each claim prior to this inventionin the portion of each claim that is disposed before the terms "theimprovement" and sets forth what is believed to be new in each claimaccording to this invention in the portion of each claim that isdisposed after the terms "the improvement" whereby it is believed thateach claim sets forth a novel, useful and unobvious invention within thepurview of the Patent Statute.

What is claimed is:
 1. In a method of making a belt construction mainlyof thermoplastic material and having opposed sides one of whichcomprises a plurality of teeth and the other of which comprises abacking portion of said belt construction, said thermoplastic materialbeing of the type of material that has only been used to form a toothedbelt construction by having been heated to a temperature above itsmelting temperature so as to be in a molten condition thereof and thenbeen injection molded while in said molten condition thereof to formthat toothed belt construction, the improvement comprising the steps ofdisposing one layer of said thermoplastic material about the outerperipheral surface of a building drum that has said outer peripheralsurface thereof defined by alternating teeth and grooves, and thenforcing said one layer of thermoplastic material toward said drum whilethe temperature of said one layer of thermoplastic material is above itssoftening temperature and below its melting temperature so as to causepart of said one layer of thermoplastic material to exude into saidgrooves to form at least the major portion of said plurality of teethand to cause another part of said one layer of thermoplastic material toform at least the major portion of said backing portion of said beltconstruction.
 2. A method as set forth in claim 1 and comprising thestep of heating said one layer of thermoplastic material to saidtemperature thereof that is above its softening temperature and belowits melting temperature.
 3. A method as set forth in claim 2 wherein thestep of forcing said one layer of thermoplastic material toward saiddrum comprises the step of subjecting said one layer of thermoplasticmaterial to steam pressure which not only provides a force on said onelayer of thermoplastic material toward said drum but also provides atleast part of the step of heating said one layer of thermoplasticmaterial.
 4. A method as set forth in claim 1 and comprising the step ofdisposing fabric material on said drum before disposing saidthermoplastic material thereon so that said fabric material will form atleast part of said teeth of said belt construction.
 5. A method as setforth in claim 4 wherein the step of disposing fabric material on saiddrum causes said fabric material to line said grooves of said drumbefore said thermoplastic material is disposed thereon.
 6. In a methodof making a belt construction mainly of thermoplastic material andhaving opposed sides with reinforcing tensile means between said opposedsides one of which comprises a plurality of teeth and the other of whichcomprises a backing portion of said belt construction, saidthermoplastic material being of the type of material that has only beenused to form a toothed belt construction by having been heated to atemperature above its melting temperature so as to be in a moltencondition thereof and then been injection molded while in said moltencondition thereof to form that toothed belt construction, theimprovement comprising the steps of disposing one layer of saidthermoplastic material about said reinforcing tensile means that hasbeen wound on the outer peripheral surface of a building drum that hassaid outer peripheral surface thereof defined by alternating teeth andgrooves, and then forcing said one layer of thermoplastic materialtoward said drum while the temperature of said one layer ofthermoplastic material is above its softening temperature and below itsmelting temperature so as to cause part of said one layer ofthermoplastic material to exude through said tensile means and enterinto said grooves to form at least the major part of said plurality ofteeth and to cause another part of said one layer of thermoplasticmaterial to form at least the major portion of said backing portion ofsaid belt construction.
 7. A method as set forth in claim 6 andcomprising the step of heating said one layer of thermoplastic materialto said temperature thereof that is above its softening temperature andbelow its melting temperature.
 8. A method as set forth in claim 7wherein the step of forcing said one layer of thermoplastic materialtoward said drum comprises the step of subjecting said one layer ofthermoplastic material to steam pressure which not only provides a forceon said one layer of thermoplastic material toward said drum but alsoprovides at least part of the step of heating said one layer ofthermoplastic material.
 9. A method as set forth in claim 6 andcomprising the step of disposing fabric material on said drum beforedisposing said reinforcing tensile means thereon so that said fabricmaterial will form at least part of said teeth of said beltconstruction.
 10. A method as set forth in claim 9 wherein the step ofdisposing fabric material on said drum causes said fabric material toline said grooves of said drum before said reinforcing tensile means isdisposed thereon.